1. Field of the Invention
The invention relates to the field of positioning devices, and more particularly, to a device for positioning a cable end and an associated connector during inductive heat soldering of the cable to the connector.
2. Prior Art
An electrical connector having a bore or channel for receiving a cable end therein is generally terminated to the cable by crimping or soldering. In a known method of soldering an electrical connector to a cable, the connector includes a solder preform disposed at a selected location along the bore. With the cable end situated in the bore, a portion of the connector including the solder preform is heated in an inductive heating process to melt the solder preform, whereby the solder reflows around the cable end and, upon cooling, provides a secure electrical connection between the cable and connector.
The inductive heating process utilizes a self-regulating temperature source which, when energized by a constant amplitude, high frequency alternating current, generates thermal energy and achieves a resulting constant temperature. Such a temperature can be selected to be just higher than the ideal temperature at which solder melts. The self-regulating temperature source is disclosed in U.S. Pat. Nos. 4,256,945; 4,623,401; 4,659,912; 4,695,713; 4,701,587; 4,717,814; and 4,745,264, which are incorporated herein by reference. The self-regulating temperature source employs a substrate of copper or copper alloy or other conductive material of low electrical resistivity, negligible magnetic permeability and high thermal conductivity. Deposited on one surface thereof is a thin layer of thermally conductive magnetic material such as iron, nickel or a nickel-iron alloy having a much higher electrical resistance and magnetic permeability than the substrate material. When a radio frequency current is passed through a conductor in close proximity to such a two layer structure, thermal energy is generated in the magnetic surface layer until the temperature of the surface layer approaches the Curie temperature of the magnetic material. As the Curie temperature is approached, declining magnetic permeability of the surface layer causes a reduction in thermal energy generation until, at the Curie temperature, thermal energy generation ceases. At the same time, the thermally conductive substrate drains thermal energy from the surface layer, which tends to reduce the temperature of the substrate and increase its magnetic permeability, thereby increasing thermal energy generation so as to offset thermal losses to the substrate. By carefully selecting the particular magnetic material and conductive material and the thicknesses thereof, one can construct a self-regulating heat source which maintains a certain maximum temperature at a given current frequency. The maximum temperature is selected to be slightly above the solder melting temperature so as to achieve solder reflow while preventing excessive heat generation which could harm delicate electrical components.
In order to solder a connector to a cable using the inductive heating process, the connector and cable must be held in respective alignment while a portion of the connector is exposed to a high-frequency current field. Standard connectors are fairly small, and it is difficult to hold the connector and cable in alignment and to precisely target a heating portion of the connector with the high-frequency current field. The heating portion of the connector is generally at the cable receiving end of the connector. Prior art devices for positioning the connector have utilized an end face of the connector opposite from the cable receiving end as a locating surface of the connector in order to provide good access to the heating portion. A problem with these devices is that a different locator must be used for a right-angled connector than for a straight connector. Also, it is often desirable to produce short lengths of U-shaped jumper cable having a connector attached at each end. After a connector is attached to one end, the attached connector can interfere with positioning members of a holding device and prevent proper positioning of a connector to be attached to the other end of the cable. A simple device is needed which can readily position a cable end and an associated straight or angled connector during inductive heat soldering of the connector to the cable, and which will enable a connector to be soldered to both ends of a short U-shaped jumper cable.